In many conveying devices such as, for example, elevator installations, cranes or hoists use is made of belt-shaped support means. These support means in general comprise several tensile carriers which consist of steel wires and which absorb the tensile forces to be accepted by the support means. The tensile carriers are usually surrounded by a casing of synthetic material. The casing protects the tensile carriers from, for example, mechanical wear, because the support means are frequently guided over deflecting points. In addition, the casing improves the traction of the support means on deflecting or drive rollers and fixes the arrangement of the tensile carriers with respect to one another.
Such support means within a conveying device are often a safety-critical component. Failure or breakage thereof can lead to dropping down of the object to be conveyed. This can lead to significant damage to articles or harm to persons. For this reason, check units are used in conveying devices which check, in particular, the mechanical state of the tensile carriers. Damage to the tensile carriers accepting the forces shall thereby be able to be recognized in good time so that the support means in the case of damage can be exchanged in order to help prevent failure of the conveying device.
The tensile carriers are surrounded by the electrically insulating casing of synthetic material. For performance of a test of the state of the tensile carriers in some methods a contacting of a contact element with the tensile carrier is required. In this known method with the help of the contact element an electric current is conducted through the tensile carriers and serves as a test current establishing the state of the tensile carriers. Apart from that, other test methods which do not operate with electrical current, for example ultrasound, also come into consideration.